1. Field of the Invention
The present invention relates to a wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor. In particular, the invention relates to a power-saving wireless network with packets buffering performance, a packet transmitting method for use in the wireless network, and a computer readable medium therefor.
2. Descriptions of the Related Art
Low speed wireless communication devices are highly noticed recently in the fields of household appliances, toys, industries, security services, and medical care. For the characteristics of low cost, low power consumption, and easily disposed of those low speed wireless communication devices, they are especially proper to be applied in a broad service area with little maintenance. Among various low speed wireless communication protocols, the most representative standard among them is IEEE 802.15.4/ZigBee.
In a ZigBee wireless network, the coverage is limited due to the restricted radio wave strength. When a large service area is desired, access points are usually needed to be disposed to form a union to provide better radio wave coverage.
As shown in FIG. 1, a conventional wireless network 1 is illustrated. The wireless network 1 comprises a personal area network coordinator (PAN coordinator) 10, a sending node 11, a receiving node 13, a first access node 12, a second access node 14, a third access node 16, and a fourth access node 18. When the sending node 11 requires sending a packet to the receiving node 13, the packet has to be transmitted by the access nodes 12, 14, 16 and 18 to the receiving node 13, due to the limited radio wave coverage. A transmitting path 1a for illustrating the transmitted packet is approximately indicated in FIG. 1.
However, for the purpose of power-saving, nodes in the ZigBee wireless network frequently enter into a sleeping mode. For example, the node may shut down the wireless antenna which may be the most power consuming element thereof. Meanwhile, as shown in the transmitting path 1a, the packet would not be received by the receiving node 13 correctly, and thus, the packet would be lost. To solve the problem, generally, there are two conventional solutions. One is to temporarily store the packet in the neighbor nodes (e.g. the fourth access node 18), and the other is to shorten the sleep period of the receiving node 13.
In point of the first solution, the memory size of the access nodes would be a key factor. The memory size of the access node needs to be increased for providing sufficient space to store packets temporarily. Furthermore, when an access node corresponds to a plurality of receiving nodes, the memory size thereof would be inestimable and then the costs of constructing the wireless network would be raised. Moreover, the conventional technology uses the MAC (medium access control) layer of the packet. In accordance with the conventional ZigBee standards, it only stipulates that “at least reserving a packet” in the MAC layer. Just a few companies develop technologies which support seven-packet storage. Nevertheless, the problem of memory requirements will definitely occur in some situations and result in loss of packets and restrict the applications of the ZigBee wireless network as well.
In point of the second solution, shortening the sleep periods of the receiving node would simultaneously shorten the power-saving period of the receiving nodes. It would be a disadvantage to construct a power-saving wireless network. Furthermore, the temporary period of the packets is three seconds by present ZigBee standards. It could simply infer that the receiving nodes have to return to working mode in three seconds (e.g. waking up every two seconds). Thus, power-saving efficiency of the nodes would be greatly reduced.
Given the above, a novel power-saving wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor need to be developed in this field.